Transcript No Slide Title

CSCI 4211
Introduction to Computer Networks
Jeopardy Review
Rules
• Up to six students form a group.
• After the questions show up, the team
raises the # card first to get called on
and MUST start to answer the question
when TA calls on them with in 10 seconds
(otherwise lose 100 points)
• Each team gets one AND ONLY ONE
answer per question
Difference from normal Jeopardy! game
• Questions are given, you provide the answer.
(not vise versa)
• The group that answers correctly has the
exclusive right to answer the next question.
• At most answer two questions for a group.
After that, all groups are allowed to compete
for the next question.
• Only The Jeopardy Round and Final Jeopardy
round
Other logistics
• Cheng is the host, and Guobao is in charge of
book keeping on white board (one score per
group).
• To ensure the smoothness of the game, TAs
make the FINAL decision whether an answer
is correct or not, we can resolve
disagreement later.
Extension at stake
The winning teams (two teams)
win 24 hours for late
submission of an assignment.
Click to begin.
Level
Category A Category B Category C
IP AddressingIP Forwarding Routing
Easy
100 $
100 $
100 $
Medium
200 $
200 $
200 $
Hard
300 $
300 $
300 $
Daunting
400 $
400 $
400 $
Almost
Impossible
500 $
500 $
500 $
Question 1a
In a CIDR format 192.168.2.0/12
What is the meaning of 12?
Answer 1a
The length of network prefix
BACK
Question 2a
(T/F) One machine (such as router,
host, etc.) can only have one IP
address.
Answer 2a
False. IP addresses are associated
with interfaces. Since one machine
may have multiple interfaces, it can
have multiple IP addresses.
BACK
Question 3a
A widely used technique for
alleviating the IPv4 address shortage
is _____
Answer 3a
NAT
Network Address Translation
mapping mulitple intranet IP addresses to
a single internet IP address using
different port numbers
BACK
Question 4a
How many subnets are shown below?
Answer 4a
8
BACK
Question 5a
How many Class C Internet addresses
would an organization need in order to
number 2000 hosts ( classful
addressing)?
Answer 5a
2^8-2 = 254 hosts each Class C
address.
2000/254 = 7.87  8.
BACK
Question 1b
Name two network service models.
Answer 1b
Datagram and Virtual Circuit
BACK
Question 2b
Provide one key difference between
virtual circuit model and datagram
model.
Answer 2b
Routing: datagram model determines next to
each destination a priori, while virtual circuit
model determines a path from source to each
destination at “call” setup time.
Forwarding: in datagram model, destination
address is in packet header, used at each hop to
look up for next hop. In virtual circuit model,
each packet carries “tag” or “label” (virtual
circuit id, VCI), which determines next hop.
BACK
Question 3b
Name four fields in IP datagram.
Answer 3b
IP protocol version, header length,
Type of Service, total length,
identification, flags, fragment offset,
time to live, protocol type, source IP
address, destination IP address…
BACK
Question 4b
A packet with destination IP address 11001000
00010111 00011000 10101010 should go to
interface ______?
Answer 4b
Interface 1
BACK
Question 5b
4100 byte datagram
MTU = 1500 bytes
Answer 5b
BACK
Question 1c
(T/F) Link state routing is a centralized
routing algorithm, and distance vector
routing is a distributed routing
algorithm.
Answer 1c
False. Both of link state routing and
distance vector routing are distributed
routing algorithms.
BACK
Question 2c
Provide one key difference of link state
routing and distance vector routing.
Answer 2c
•
•
•
•
•
•
Link State
vs
Tells everyone about
neighbors
Controlled flooding to
exchange link state
Dijkstra’s algorithm
Each router computes its
own table
May have oscillations
Open Shortest Path First
(OSPF)
Distance Vector
• Tells neighbors about
everyone
• Exchanges distance
vectors with neighbors
• Bellman-Ford algorithm
• Each router’s table is
used by others
• May have routing loops
• Routing Information
Protocol (RIP)
BACK
Question 3c
Name two relationships between
Autonomous Systems.
Answer 3c
Customer-Provider
Peering
BACK
Question 4c
How the BGP Protocol detects routing loops?
Answer 4c
BGP use Path Vector: A sequence of AS
numbers
If the same AS number appears more
than once, there is a loop.
BACK
Question 5c
Why does YouTube want to peer with
various so-called “eye-ball” ISPs,
such as AOL, Comcast?
Answer 5c
Peers provide transit between their respective
customers, and often time they do not charge each
other for carrying traffic. YouTube currently pays a
lot to its transit providers (customer-provider
relationship), such as AT&T and Qwest, for
carrying its content to its users. If it can peer with
eye-ball ISPs, YouTube will save a huge amount of
money by directly delivering content traffic to those
ISPs. Eye-ball ISPs can also benefit for the same
reason.
BACK
Make your wager up to what you have
Write down the wager along with the
answer on the back of the index card.
Finish in 3 minutes!!!
Final Question
Compute the shortest path from s to all network
nodes.
Final Answer